Red light development of free radical system within 50 nanometers

ABSTRACT

THE PROCESS DESCRIBED IN UNITED STATES PAT. 3,510,300 IS GREATLY OIMPROVED BY RESTRICTING THE RADIATION USED FOR DEVELOPING VISIBLE IMAGES IN NON-SILVER FREE RADICAL FILM TO A VERY NARROW BAND OF WAVELENGTHS NOT BROADER THAN 50 NONOMETERS.   D R A W I N G

v 1973 F. w. SCHMIDT 3,732,098

RED LIGHT DEVELOPMENT OF FREE RADICAL SYSTEM WITHIN 50 NANOMETERS Filed Sept. 22 1971 730nm 1 lOnm zo'ro 25nm pk BAND WIDTH 1 l l l l 600 100 I150 800 900 I000 uoo 1200 I300 I400 I500 I600 120 WAVELENGTH (NANOMETERS) l l l O O O O O 8 K r N AJJSNBlNl NOIlVIOVB HAHN 3H INVENTOR FREDERICK W. SCHMIDT BY jaiw ATTORNEY United States Patent U.S. CI. 9648 R 3 Claims ABSTRACT OF THE DISCLOSURE The process described in United States Pat. 3,510,300 is greatly improved by restricting the radiation used for developing visible images in non-silver free radical film to a very narrow band of wavelengths not broader than 50 nanometers.

This invention relates to the development of visible images in non-silver free radical photosensitive films containing an organic halogen compound in which at least three halogen atoms are attached to a single carbon atom and containing a dye salt progenitor compound as described, for example, in United States Pat. 3,510,300 and in other recently issued patents and publications.

More particularly, it relates to the development of visible images by the use of radiation in a very narrow band of wavelengths preferably not broader than 50 nanometers, the wavelengths of such radiation being dependent upon the specific composition of the photosensitive material being processed.

A principal object of the invention is to increase the etficiency of the dry-working process described in the above noted patent.

A further object is to diminish the dose of radiation required to produce useful images in the process of said patent.

Still a further object of the invention is to diminish the occurrence of fog or other detrimental background in the finished film.

These and other objects of the invention will become more fully understood from the description which follows taken with the drawing which is a figure showing the relative spectral emission utilized in the present invention as compared with the relative spectral emission utilized in the prior art.

As shown in'the drawing, the radiation passed by a prior art filter such as a Wratten 89B filter includes a large amount of energy at wavelengths of more than 750 nm., whereas the radiation passed by a band filter used according to the present invention is in the band 730 nm. nm.

By the use of a narrow bandpass interference filter, the radiation to which the photosensitive material is exposed no longer contains large amounts of unwanted and ineffective radiation in the visible and in the infrared. The radiation outside the narrow band is unwanted because it does not make as great a differentiation between amplification of the latent image and fog. The shorter wavelengths during development cause fogging because the film has its basic sensitivity in that area. Although the films useful sensitivity might be limited to the blue and ultraviolet bands, it will have residual sensitivity of decreasing amounts into the green and red. Experiments with a series of narrow band interference filters can clearly identify the amount of differentiation between image and fog development relative to the visible and IR spectrum. As the wavelengths longer than the optimum are lengthened, the image to fog ratio gradually deteriorates. The image will not develop as well because the optimum has been passed. Fog development will reach a base amount and might actually increase due to thermal initiation.

Use of a narrow band of radiation for development yields higher film performance plus better energy efficiency. The latent image/ fog ratio is degraded least when a narrow band of light peaking at the appropriate wavelength is used. Higher film speeds and better gamma control result. With an interference filter, the light intensity at the film plane can be reduced more than 100 times compared to the best previous light sources and still get comparable development in the same time.

The following example compares the energy provided to develop unit density in a film formulated according to Example 4 of U.S. Pat. 3,510,300, using a Wratten It will be understod that for other formulations, other bands of radiation must be selected in order to achieve the desired results.

Further, the means used to provide the radiation for development may be other suitable devices such as a light emitting diode or a laser, which emits radiation in a narrow band, instead of the narrow bandpass interference filter.

One such means is described in a copending application filed concurrently herewith.

Having now described the invention in accordance with the patent statutes, it is not intended that it be limited except as may be required by the appended claims.

What is claimed is:

1. In a dry process for developing a visible image in a non-silver free radical photosensitive film containing an organic halogen compound in which at least three halogen atoms are attached to a single carbon atom and a dye salt progenitor compound wherein the image is developed by exposing the photosensitive film to a dose of red light radiation, the improvement which comprises: developing said visible image by exposing said film to radiation which consists entirely of radiation in a narrow band not broader than 50 nanometers which effects development of the visible image, with greatest effectiveness, the wavelengths shorter than those in said band being visible radiation to which the film exhibited sensitivity before the exposure by which the latent image was formed and hence being radiation which would cause fogging and the wavelengths longer than those in said band being in the infrared and causing thermal fog in said film.

2. The process of claim 1 in which the developing radiation is passed through a narrow bandpass interference filter.

3. The process of claim 1 in which the radiation applied to the film is obtained from a source consisting of at least one light emitting diode.

References Cited UNITED STATES PATENTS 3,573,046 3/1971 Fotland et al. 9648 3,510,300 5/1970 Fotland et al. 96-27 NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR, Assistant Examiner U.S. Cl. X.R. 9627 R, R 

